Enveloping device and vertical heat-treating apparatus for semiconductor process system

ABSTRACT

The process tube of a vertical heat-treating apparatus for semiconductor wafers has a port at the bottom to be opened and closed by a lid. A sealing mechanism is arranged to seal the connecting portion between the flange of the port and the flange of the lid. The flanges are provided with annular mirror surfaces on the inner side, which face and contact each other to form an inner seal. The flanges are also provided with annular counter surfaces on the outer side, which face each other with a gap therebetween. A metal sheet member is arranged in the gap such that an outer seal is formed by the metal sheet member and the counter surfaces. The metal sheet member has sheets vacuum-stuck onto the counter surfaces, respectively. A buffer space is formed between the inner and outer seals, and is vacuum-exhausted by an exhaust unit.

This application is a divisional of Ser. No. 09,375,466 filed Aug. 17,1999 U.S. Pat. No. 6,142,773.

BACKGROUND OF THE INVENTION

The present invention relates to an enveloping device and a verticalheat-treating apparatus for a semiconductor process system, andparticularly to a heat-treating apparatus which is capable of performingprocesses, such as oxidation, diffusion, and CVD (Chemical VaporDeposition), in series. The term “semiconductor process” used hereinincludes various kinds of processes which are performed to manufacture asemiconductor device or a structure having wiring layers, electrodes,and the like to be connected to a semiconductor device, on a targetsubstrate, such as a semiconductor wafer or an LCD (Liquid CrystalDisplay) substrate, by forming semiconductor layers, insulating layers,and conductive layers in predetermined patterns on the target substrate.

In a process of manufacturing a semiconductor device, various kinds ofheat-treating apparatuses are used for subjecting a semiconductor waferto processes, such as oxidation, diffusion, CVD, and annealing. Theheat-treating apparatuses are roughly categorized into two types, i.e.,a single-substrate-processing type in which wafers are processed one byone in a process chamber, and a batch-processing type, which is of ahorizontal type or a vertical type, in which wafers are processed alltogether in a process chamber.

For example, a vertical CVD apparatus of the batch-processing typeemploys a vertically long process chamber for accommodating a boat inwhich a number of wafers are stacked with a gap therebetween. Theprocess chamber is constituted of a cylindrical reaction tube or processtube made of quartz and a cylindrical manifold made of a metal, which isattached to the bottom of the reaction tube and has a gas inlet and agas outlet. The manifold is provide with a port at its bottom, throughwhich the wafer boat is loaded and unloaded to and from the reactiontube, while the wafer boat is supported on a metal lid for opening andclosing the port. O-rings are used for connecting portions of the partsconstituting the process chamber to ensure that the process chamber ishighly airtight.

On the other hand, a vertical diffusion or oxidation apparatus of thebatch-processing type also employs a vertically long process chamber foraccommodating a wafer boat. The process chamber is constituted of areaction tube made of quartz having a gas inlet and a gas outlet on itsside wall. The reaction tube is provide with a port at its bottom,through which the wafer boat is loaded and unloaded to and from thereaction tube, and a quartz lid for opening and closing the port. Inother words, the process chamber is entirely made of quartz to ensurethat the process chamber is highly heat-resistant and highlycorrosion-resistant.

The CVD apparatus described above is capable of handling a process usinga high vacuum condition, but does not suit a process using a hightemperature or a corrosive gas, because the apparatus employs severalO-rings and the metal manifold. On the other hand, the diffusion oroxidation apparatus described above is capable of handling a processusing a high temperature or a corrosive gas, but does not suit a processusing a high vacuum condition, because the apparatus is not highlyairtight.

Accordingly, where processes of oxidation, diffusion, and CVD are to beperformed in series in a conventional semiconductor process system,heat-treating apparatuses respectively dedicated to the differentprocesses have to be arranged. In this case, a wafer has to betransferred among the apparatuses for respective processes, therebyentailing a waste of time as well as degradation in the quality of afilm formed on the wafer.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide an enveloping devicefor a semiconductor process system, which can be adapted to variouskinds of conditions.

Another object of the present invention is to provide a verticalheat-treating apparatus for a semiconductor process system, which allowsprocesses each using a heat treatment, such as oxidation, diffusion, andCVD, to be performed in series in the apparatus.

According to a first aspect of the present invention, there is providedan enveloping device having a sealing mechanism for a semiconductorprocess system, comprising:

a casing having first and second parts detachably assembled to envelop apressure-reduced space;

a member configured to apply a mechanical force to join the first andsecond parts;

a first flange arranged on the first part, and being provided with alooped first mirror surface, and a looped first counter surface arrangedaround the first mirror surface, the first mirror surface having asurface roughness of Ra (mean surface roughness)=0.06 μm or less;

a second flange arranged on the second part, and being provided with alooped second mirror surface, and a looped second counter surfacearranged around the second mirror surface, the second mirror surfacehaving a surface roughness of Ra=0.06 μm or less, the first and secondmirror surfaces facing and contacting each other to form an inner sealfor substantially airtightly sealing the pressure-reduced space, thefirst and second counter surfaces facing each other with a gaptherebetween;

a looped seal member arranged in the gap such that an outer seal isformed by the first and second counter surfaces and the seal member, anda looped buffer space, substantially airtightly closed, is formedbetween the inner and outer seals; and

a buffer exhaust mechanism configured to exhaust and set the bufferspace to a pressure-reduced state.

According to a second aspect of the present invention, there is provideda vertical heat-treating apparatus for subjecting a plurality of targetsubstrates to a heat treatment at the same time in a semiconductorprocess system, comprising:

a process tube forming a pressure-reduced process space foraccommodating the target substrates, and having a port at a bottom forloading and unloading the target substrates, and a first flangesurrounding the port, the first flange being provided with a loopedfirst mirror surface, and a looped first counter surface arranged aroundthe first mirror surface, the first mirror surface having a surfaceroughness of Ra=0.06 μm or less;

a lid configured to open and close the port, and having a second flangefor sealing the process space in cooperation with the first flange, thesecond flange being provided with a looped second mirror surface, and

a looped second counter surface arranged around the second mirrorsurface, the second mirror surface having a surface roughness of Ra=0.06μm or less, the first and second mirror surfaces facing and contactingeach other to form an inner seal for substantially airtightly sealingthe process space, the first and second counter surfaces facing eachother with a gap therebetween;

a looped seal member arranged in the gap, and having a looped firstsheet in contact with the first counter surface, a looped second sheetin contact with the second counter surface, and a looped connectingportion airtightly connecting the first and second sheets to each other,such that an outer seal is formed by the first and second countersurfaces and the seal member, and a looped buffer space, substantiallyairtightly closed, is formed between the inner and outer seals;

a suction mechanism configured to vacuum-stick the first and secondsheets onto the first and second counter surfaces, respectively, andincluding suction holes formed in the first and second flanges to haveopenings corresponding to the first and second sheets, respectively;

a buffer exhaust mechanism configured to exhaust and set the bufferspace to a pressure-reduced state;

a holder configured to hold the target substrates to be stacked with agap therebetween in the process tube, the holder being loaded andunloaded to and from the process tube through the port while holding thetarget substrates;

an elevating mechanism configured to move up and down the lid along withthe holder, the second flange of the lid being pressed against the firstflange of the process tube by the elevating mechanism;

a heater configured to heat the process tube and arranged around theprocess space;

a supply mechanism configured to supply a process gas into the processspace; and

a main exhaust mechanism configured to exhaust and set the process spaceto a pressure-reduced state.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention, and together with the general description given above andthe detailed description of the preferred embodiments given below, serveto explain the principles of the invention.

FIG. 1 is a constitutional view mainly showing a vertical cross-sectionof the main part of a vertical heat-treating apparatus according to anembodiment of the present invention;

FIG. 2 is an enlarged cross-sectional view showing the part near a gasinlet of the apparatus shown in FIG. 1;

FIG. 3 is a front view showing an end plate of the gas inlet shown inFIG. 2;

FIG. 4 is a cross-sectional view schematically showing the part cutalong line IV—IV in FIG. 1;

FIG. 5 is a perspective view showing an annular seal ring for sealing anannular space formed between outer and inner tubes of the apparatusshown in FIG. 1;

FIG. 6 is an enlarged cross-sectional view showing a sealing mechanismarranged near the port of the process chamber of the apparatus shown inFIG. 1; and

FIG. 7 is a perspective view for explaining the support structure forthe rotating mechanism of the apparatus shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, a vertical heat-treating apparatus includes aprocess chamber 1 which has a port 2 formed at the bottom for loadingand unloading a boat 5 holding a number of semiconductor wafers. Theport 2 is opened and closed by a lid 6 which is vertically moved by anelevating mechanism ME. For example, 150 wafers are supported in theboat 5 such that they are stacked with a gap therebetween. A gas inlet 3is formed in the side wall of the process chamber 1 and connected to agas supply unit S1 for supplying process gases into the process chamber1. A gas outlet 4 is also formed in the side wall of the process chamber1 and connected to a main exhaust unit El for exhausting the processchamber 1 and setting it to a vacuum.

The process chamber 1 has a double-tube structure consisting of an outertube 7 and an inner tube 8 arrange concentric with each other and eachformed of a vertically long cylinder which is made of a heat-resistantand corrosion-resistant material, such as quartz. The outer tube 7essentially forms a reaction tube which has a closed top and an openbottom. The inner tube 8 has an open top and an open bottom.Accordingly, a gas passage is formed in the process chamber 1 such thata process gas flows upward from the bottom of the inner tube 8 and isused for processing the wafers W, and then flows downward through anannular space 9 between the inner and upper tubes 8 and 7 and isexhausted.

In order to detachably arrange the inner and outer tubes 8 and 7, abayonet coupling structure is employed. Specifically, as shown in FIG.4, the outer surface of the inner tube 8 and the inner surface of theouter tube 7 are provided with engaging fins 10 and 11 arranged atintervals in the angular direction, so that the fins 10 and 11 canselectively overlap and engage with each other. When the engaging fins10 of the inner tube 8 are positioned between the engaging fins 11 ofthe outer tube 7 by rotating the inner tube 8 by a certain angle, theengagement between-the fins 10 and 11 is released, so that the innertube 8 can be detached from the outer tube 7. The engaging fins 10 and11 are preferably arranged at positions below the gas inlet 3 and gasoutlet 4.

The outer and inner tubes 7 and 8 are provided with outward flanges 12and 13, respectively, at the bottom. A seal ring 14 is arranged at thebottom of the annular space 9 between the outer and inner tubes 7 and 8to seal the annular space 9, so that a process gas is not allowed toleak downward from the annular space 9. As shown in FIG. 5, the sealring 14 has a C-shape with a cut 15 in the plan view, so that it cancome into contact with the inside of the outer tube 7 with a spring-likeforce.

The annular space 9 between the outer and inner tubes 7 and 8 is sealedby the seal ring 14 wherein the ring 14 is in contact with the inside ofthe outer tube 7 and is also in contact with the top surface of theflange 13 of the inner tube 8 by its own weight. A weight may bedisposed on top of the seal ring 14, so that the seal ring 14 is pressedagainst the top surface of the flange 13 of the inner tube 8. When theseal ring 14 is attached in the outer tube 7, the cut 15 becomes sosmall that leakage of a process gas through the cut 15 does not affectthe process.

In this embodiment, the outer and inner tubes 7 and 8, the lid 6, andthe seal ring 14 are all made of quartz. However, each of these membersmay be made of a material selected from the group consisting of siliconoxide (including quarts), silicon carbide, zirconium oxide, and aluminumoxide.

Piping portions P3 and P4 formed integrally with the outer tube 7 extendfrom the side wall of the outer tube 7. The piping portions P3 and P4communicate with the gas inlet 3 for supplying process gases into theprocess chamber 1, and the gas outlet 4 for exhausting the processchamber 1, respectively. The piping portions P3 and P4 of the gas inletand outlet 3 and 4 are provided with flanges 16 and 17, respectively, atthe distal ends. The piping portion P3 of the gas inlet 3 is connectedto the gas supply unit S1 through a gas introducing structure 18. Thepiping portion P4 of the gas outlet 4 is connected through an exhaustline 19 to the main exhaust unit E1 including a vacuum pump which iscapable of reducing the pressure within the process chamber 1 down toabout 10⁻⁸ Torr.

Between the piping portion P3 and the gas introducing structure 18, andbetween the piping portion P4 and the exhaust line 19, sealingmechanisms 20 of a first type for ensuring an airtight connection arerespectively arranged. On the gas inlet 3 side, the first type sealingmechanism 20 is arranged between the flange 16 of the piping portion P3of the gas inlet 3 and a flange 21 a of an end plate 21 of the gasintroducing structure 18, which are mechanically joined by a pluralityof screws BS (see FIG. 2). On the gas outlet 4 side, the first typesealing mechanism 20 is arranged between the flange 17 of the pipingportion P4 of the gas outlet 4 and a flange 27 of the exhaust line 19,which are mechanically joined by a plurality of screws. Instead of thescrews, a clamp for sandwiching two flanges may be used for mechanicallyjoining the flanges. Because the two sealing mechanisms 20 of the firsttype respectively arranged on the gas inlet 3 side and the gas outlet 4side have substantially the same structure, only the mechanism 20 on thegas inlet 3 side will be explained below.

Specifically, as shown in FIG. 2, in order to constitute the first typesealing mechanism 20 on the gas inlet 3 side, the flange 16 is providedwith a first mirror surface 23 a having an annular or looped shapearranged on the inner side, and a first counter surface 25 a having anannular or looped shape arranged around the first mirror surface 23 a.Similarly, the flange 21 a is provided with a second mirror surface 23 bhaving an annular or looped shape arranged on the inner side, and asecond counter surface 25 b having an annular or looped shape arrangedaround the second mirror surface 23 b.

The first and second mirror surfaces 23 a and 23 b each have a surfaceroughness of Ra (mean surface roughness)=0.06 μm or less. The first andsecond mirror surfaces 23 a and 23 b face and contact each other to forman inner seal for substantially airtightly sealing the pressure-reducedspace within the piping portion P3. The first and second countersurfaces 25 a and 25 b face each other with a gap therebetween.

In the gap between the first and second counter surfaces 25 a and 25 b,an O-ring 24 made of, e.g., a fluoride base rubber, is arranged, so thatan outer seal is formed by the first and second counter surfaces 25 aand 25 b and the O-ring 24. An annular or looped buffer space,substantially airtightly closed, is formed between the inner and outerseals. The buffer space is connected through a hole 26 formed in theflange 21 and a pipe 39 to a buffer exhaust unit E2, including aturbo-molecular pump or the like, for exhausting the buffer space andsetting it at a pressure-reduced state. This arrangement presents asealing structure which is highly airtight and entails a low out-gas,i.e., a low gas emission from the O-ring 24, because the O-ring 24 isnot exposed to the inside of the process chamber.

As shown in FIGS. 2 and 3, the gas introducing structure 18 is designedsuch that a plurality of conduits 28 are arranged in the piping portionP3 of the gas inlet 3. The conduits 28 include a plurality of, e.g., 8,conduits 28 for supplying different gases for processes, such asdiffusion, CVD, and the like, and a conduit 28 for inserting athermometer for detecting the temperature in the process chamber 1. Onlyone piping portion P3 is commonly used for the plurality of conduits 28,the corresponding structure of the process chamber 1 becomes simple. Theconduits 28 airtightly penetrate the end plate 21, which is made of ametal, such as stainless steel, of the gas introducing structure 18. Theinner surface of the end plate 21 is covered with a corrosion-resistantcover 29 of, e.g., quartz, to protect the end plate 21 from corrosion.

The conduits 28 for supplying process gases are directly connected tothe inside of the inner tube 8. Specifically, as shown in FIG. 2, theend plate 21 is provided with gas supply metal nozzles 30, and thequartz pipes 28 a fit on the metal nozzles 30 and are connected thereto.Each of the metal nozzles 30 is provided with a plurality of slits 31 atthe distal end, so that the distal end comes into contact with theinside of the quartz pipe 28 a with a spring-like force.

The corrosion-resistant cover 29 is formed of a circular body having asize to fit on the inside of the piping portion P3 of the gas inlet 3,with the outer edge extending onto the end plate 21. In order to causethe corrosion-resistant cover 29 to fit on the end plate 21, one end ofa fixing bar 32 made of a metal, such as stainless steel, is attached tothe end plate 21 by a screw 33. The other end of the fixing bar 32 isattached to the corrosion-resistant cover 29 by a screw 34. Thecorrosion-resistant cover 29 is further provided with sleeves 35extending in the longitudinal direction of the piping portion P3 toinsert the conduits 28 therein, respectively.

In order to prevent a corrosive gas from entering a space 36 between theend plate 21 and the corrosion-resistant cover 29, the end plate 21 isprovided with a pipe 37 and a hole 38 for supplying an inactive gas,such as nitrogen (N₂), into the space 36. On the outside of the endplate 21, a panel heater 40 capable of heating to a predeterminedtemperature of, e.g., about 200° C., is arranged to prevent a reactionproduct from adhering onto the inside of the end plate 21.

The side wall of the inner tube 8 is provide with through holes 41 eachof which allows the distal end of the quartz pipe 28 a to looselypenetrate therethrough, so as to accommodate a low tolerance of thequartz members while reliably supplying process gases into the innertube 8. An enlarged portion 42 is arranged at the distal end of thequartz pipe 28 a to seal the through hole 41. The enlarged portion 42 ispreferably arranged to be in contact with the inside of the inner tube8, but may be arranged to be in contact with the outside of the innertube 8.

An annular frame 43 is arranged around the flange 12 of the outer tube 7to support the outer tube 7. The frame 43 is supported by a base plate44 through support rods 45. A flange clamp 46 is attached to the frame43 to fix the flange 12 of the outer tube 7. A heater 47 is arranged onthe base plate 44 to surround the process chamber 1 and to heat theinside of the process chamber 1 to a predetermined temperature of, e.g.,from about 300° C. to 1000° C., under control.

Between the port 2 at the bottom of the outer tube 7 and the lid 6 foropening and closing the port 2, a sealing mechanism 48 of a second typefor ensuring an airtight connection is arranged. The sealing mechanism48 of the second type is arranged between the flange 12 around the port2 and a flange 6a of the lid 6 which is mechanically pressed against theflange 12 by the elevating mechanism ME.

Specifically, as shown in FIG. 6, in order to constitute the second typesealing mechanism 48, the flange 12 is provided with a first mirrorsurface 49 a having an annular or looped shape arranged on the innerside, and a first counter surface 51 a having an annular or looped shapeand a domed cross-section, arranged around the first mirror surface 49a. Similarly, the flange 6 a is provided with a second mirror surface 49b having an annular or looped shape arranged on the inner side, and asecond counter surface 51 b having an annular or looped shape and adomed cross-section, arranged around the second mirror surface 49 b.

The first and second mirror surfaces 49 a and 49 b each have a surfaceroughness of Ra=0.06 μm or less. The first and second mirror surfaces 49a and 49 b face and contact each other to form an inner seal forsubstantially airtightly sealing the pressure-reduced space within theprocess chamber 1. The first and second counter surfaces 51 a and 51 bface each other with a gap therebetween.

In the gap between the first and second counter surfaces 51 a and 51 b,a metal sheet member 50 is arranged, so that an outer seal is formed bythe first and second counter surfaces 51 a and 51 b and the metal sheetmember 50. The metal sheet member 50 has an annular or looped firstsheet 50 a in contact with the first counter surface 51 a, an annular orlooped second sheet 50 b in contact with the second counter surface 51b, and an annular or looped connecting portion 50 c airtightlyconnecting the first and second sheets 50 a and 50 b to each other. Themetal sheet member 50 may be fabricated by welding and airtightlyconnecting the inner edges of the two sheets 50 a and 50 b, made ofstainless steel, to each other to form the connecting portion 50 c.

The first and second sheets 50 a and 50 b are vacuum-stuck onto thefirst and second counter surface 51 a and 51 b by a suction mechanism52. The suction mechanism 52 includes annular or looped suction grooves53 a and 53 b formed in the flanges 12 and 6a to have openingscorresponding to the first and second sheets 50 a and 50 b,respectively. The suction grooves 53 a and 53 b are connected to anexhaust unit E3 including a vacuum pump or the like, through exhaustsholes 54 formed in the flanges 12 and 6 a, respectively.

An annular or looped buffer grooves 55 a and 55 b are formed on theinner sides of the first and second counter surface 51 a and 51 b,respectively.

Consequently, an annular or looped buffer space constituted mainly ofthe annular buffer grooves 55 a and 55 b and substantially airtightlyclosed is formed between the inner and outer seals. The buffer space isconnected through a hole 55 c formed in the flange 12 to a bufferexhaust unit E4, including a turbo-molecular pump or the like, forexhausting the buffer space and setting it at a pressure-reduced state.

As shown in FIG. 6, the buffer exhaust unit E4 of the second typesealing mechanism 48 has an exhaust line L4 which is connected by abypass L41 to the exhaust line L1 of the main exhaust unit El forexhausting the process chamber 1. The bypass L41 is provided with avalve V41 while the exhaust line L4 is provided with a valve V4immediately before the buffer exhaust unit E4. Consequently, the bufferspace of the second type sealing mechanism 48 can be exhaustedselectively by either one of the buffer exhaust unit E4 and the mainexhaust unit E1, by switching the valves V4 and V41.

Where the process pressure in the process chamber 1 is set at a highvacuum of about 10⁻⁷ Torr, the buffer space (grooves 55 a and 55 b) isset at a pressure of from about 10⁻⁴ to 10⁻⁷ Torr, and the suctiongrooves 53 a and 53 b are set at a pressure of from about 10 to 10⁻²Torr. In this case, the buffer space of the sealing mechanism 48 shouldbe exhausted by the buffer exhaust unit E4. On the other hand, where theprocess pressure in the process chamber 1 is set at a pressure of fromabout 100 to 760 Torr near atmospheric pressure, the buffer space(grooves 55 a and 55 b) is set at a pressure similar to that of theprocess chamber 1, and the suction grooves 53 a and 53 b are set at apressure of from about 10 to 10⁻² Torr. In this case, the buffer spaceof the sealing mechanism 48 should be exhausted, along with the processchamber 1, by the main exhaust unit El. With this operation, it becomesunnecessary to delicately control the pressure of the buffer space ofthe sealing mechanism 48, thereby making the control easier.

On the outside of the flange 12 of the process chamber 1, e.g., on topof the flange clamp 46, and on the outside of the lid 6, e.g., on thebottom, heaters 56 and 57 are arranged, respectively. The heaters 56 and57 are capable of heating to a predetermined temperature of, e.g., about300° C. to prevent a reaction product from adhering onto the insides ofthe flange 12 and the lid 6.

The lid 6 is mounted on the tray 58, which is made of a metal, such asstainless steel and connected to the elevating mechanism ME, because thelid 6 is made of quartz and is easily broken by a locally appliedexternal force. The lid 6 is mounted on the tray 58 and moved with thetray 58 by the elevating mechanism ME in the vertical direction, whilethe metal sheet member 50 of the second type sealing mechanism 48 andthe boat 5 are supported on the lid 6.

A rotational mechanism 59 is arranged at the center of the lid 6, forrotating the boat 5 on a horizontal plane during the heat treatment ofthe wafers. In order to support the rotational mechanism 59, a pluralityof, e.g., two, reverse-L brackets 62 arranged to surround a flange 61 ofthe rotational mechanism 59 are attached to the bottom of the tray 58.As also shown in FIG. 7, each of the brackets 62 is provided with ascrew pin 60 which engages therein to be movable in a radial directionof the flange 61 of the rotational mechanism 59. On the other hand, theflange 61 of the rotational mechanism 59 is provided with verticalgrooves 64 into which the tips of the screw pins 60 are inserted. Withthis arrangement, the rotational mechanism 59 can be precisely fixed ata predetermined position without applying an overload to the lid 6.

The lid 6 is provided with an axial hole 67 into which the rotationalaxis 65 of the rotational mechanism 59 is inserted, and a boss 68integrally formed with the lid 6, which is in contact with the topsurface of the flange 61 of the rotational mechanism 59. An O-ring 69 isarranged between the boss 68 and the flange 61 of the rotationalmechanism 59 for sealing this portion. The rotational axis 65 of therotational mechanism 59 is connected to a turntable 70 arranged abovethe lid 6. A labyrinth seal 71 is arranged between the turntable 70 andthe lid 6. The boat 5 is mounted on the turntable 70 through aninsulating cylinder 72, i.e., an insulating body. The insulatingcylinder 72 may be provided with a heater.

An explanation will be given to an operation of the above describedheat-treating apparatus.

First, the atmosphere in the process chamber 1 is replaced with aninactive gas, such as N₂, so as not to form a natural oxide film on thesurface of the wafers W. Then, the process chamber 1 is heated to apredetermined temperature of, e.g., 300° C., by the heater 47 underatmospheric pressure. In this state, the lid 6 is moved up by theelevating mechanism ME, along with the boat 5 holding a number of wafersW, and the metal sheet member 50 of the second type sealing mechanism 48mounted on the lid 6. When the lid 6 hits the flange 12 of the processchamber 1 to close the port 2 of the process chamber 1, the metal sheetmember 50 is placed at a predetermined position in the sealing mechanism48 and the boat 5 is placed at a predetermined position in the processchamber 1.

Then, the inside of the process chamber 1 is vacuum-exhausted by themain exhaust unit El down to a predetermined pressure of, e.g., 0.1Torr. On the other hand, the suction exhaust unit E3 and the bufferexhaust unit E4 of the sealing mechanism 48 are operated to ensure theseal between the flange 6 a of the lid 6 and the flange 12 of theprocess chamber 1.

Then, the inside of the process chamber 1 is heated to a predeterminedprocess temperature of, e.g., 850° C. by controlling the heater 47,while a predetermined process gas is supplied into the process chamber 1through the conduits 28, so that a predetermined process, such as CVD,is performed. After the process is finished, the process gas stops beingsupplied and an inactive gas starts being supplied to set the inside ofthe process chamber 1 back to atmospheric pressure. At the same time,the inside of the process chamber 1 is cooled to a predeterminedtemperature of, e.g., 300° C. by controlling the heater 47. When theprocess chamber 1 returns to atmospheric pressure and room temperature,the lid 6 is opened and the boat 5 is unloaded from the process chamber1.

As described above, in this heat-treating apparatus, the first typesealing mechanism 20, which allows no O-ring to be exposed to theinside, is arranged at each of the portions connecting the gas inlet 3and the gas outlet 4 to the gas introducing structure 18 and the exhaustline 19, respectively.

Further, the second type sealing mechanism 48, which employs no O-ring,is arranged between the port 2 and the lid 6. Since the sealingmechanisms 20 and 48 have no metal or no O-ring in contact with aprocess gas, the heat-treating apparatus has a sealed structure with ahigh heat-resistance, a high corrosion-resistance, a low out-gas, and astrong airtightness. Accordingly, the heat-treating apparatus allowsprocesses, such as oxidation, diffusion, and CVD, to be reliablyperformed in series in the apparatus, thereby improving the throughput.As a matter of course, the heat-treating apparatus may be used for asingle process, instead of serial processes.

The conduits 28 are arranged in the same piping portion P3 of the gasinlet 3. With this arrangement, the conduits 28 are concentrated at oneportion to simplify the corresponding part of the process chamber 1. Incontrast, in conventional heat-treating apparatuses, gas conduits areconnected to a process chamber independently of each other, therebycomplicating the corresponding part of the process chamber.

The inner surface of the metal end plate 21 of the gas introducingstructure 18 is covered with the corrosion-resistant cover 29. With thisarrangement, the inner surface of the end plate 21 is prevented frombeing corroded, while no metal is exposed to a process gas. The heaters40, 56, and 57 are arranged on the outside of the flange 12 of theprocess chamber 1, the lid 6 and the end plate 21. With thisarrangement, a reaction product is prevented from adhering onto theinsides of these members. Accordingly, a clean process condition ismaintained in any process, such as TEOS process or SIN process.

The process chamber 1 has a double-tube structure consisting of theouter and inner tubes 7 and 8, and the seal ring 14 is arranged at thebottom of the annular space 9 between the outer and inner tubes 7 and 8to seal the annular space 9. With this arrangement, a process gas is notleaked downward from the annular space 9. The side wall of the innertube 8 is provide with through holes 41 each of which allows the distalend of the quartz pipe 28 a of the conduit 28 to loosely penetratetherethrough, while the enlarged portion 42 is arranged at the distalend of the quartz pipe 28 a to seal the through hole 41. With thisarrangement, it is possible to accommodate a low tolerance of the quartzmembers while reliably supplying process gases into the inner tube 8.

The lid 6 is mounted on the tray 58 which is provided with the screwpins 60 to fix, from lateral sides, the rotational mechanism 59 forrotating the boat 5. With this arrangement, the rotational mechanism 59is precisely fixed without applying an overload to the quartz lid 6.

The outer and inner tubes 7 and 8 constituting the process chamber 1 arepreferably assembled to be detachable from each other for cleaning.However, since the process chamber 1 may be cleaned with a cleaning gas,the outer and inner tubes 7 and 8 may be integrated by means of, e.g.,welding, at the bottom.

The process chamber 1 is preferably formed to have a double-tubestructure to apply the features of the present invention. However,several features of the present invention may be applied to a processchamber having a single-tube structure, i.e., only an outer tube.Further, other than an apparatus for treating semiconductor wafers, thepresent invention may be applied to an apparatus for treating glasssubstrates of LCD substrates.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. An enveloping device having a sealing mechanismfor a semiconductor process system, comprising: a casing having firstand second parts detachably assembled to envelop a pressure-reducedspace; a member configured to apply a mechanical force to join saidfirst and second parts; a first flange arranged on said first part, andbeing provided with a looped first mirror surface, and a looped firstcounter surface arranged around said first mirror surface, said firstmirror surface having a surface roughness of Ra=0.06 μm or less; asecond flange arranged on said second part, and being provided with alooped second mirror surface, and a looped second counter surfacearranged around said second mirror surface, said second mirror surfacehaving a surface roughness of Ra=0.06 μm or less, said first and secondmirror surfaces facing and contacting each other to form an inner sealfor substantially airtightly sealing said pressure-reduced space, saidfirst and second counter surfaces facing each other with a gaptherebetween; a looped seal member arranged in said gap such that anouter seal is formed by said first and second counter surfaces and saidseal member, and a looped buffer space, substantially airtightly closed,is formed between said inner and outer seals; and a buffer exhaustmechanism configured to exhaust and set said buffer space to apressure-reduced state.
 2. The device according to claim 1, wherein saidseal member is formed of an O-ring.
 3. The device according to claim 1,wherein said seal member has a looped first sheet in contact with saidfirst counter surface, a looped second sheet in contact with said secondcounter surface, and a looped connecting portion airtightly connectingsaid first and second sheets to each other, and wherein said apparatusfurther comprises a suction mechanism configured to vacuum-stick saidfirst and second sheets onto said first and second counter surfaces,respectively, and said suction mechanism includes suction holes formedin said first and second flanges to have openings corresponding to saidfirst and second sheets, respectively.
 4. The device according to claim3, wherein said connecting portion of said seal member is arranged oninner sides of said first and second sheets.
 5. The device according toclaim 3, wherein said seal member consists essentially of a metal. 6.The device according to claim 1, wherein each of said casing and saidfirst and second flanges consists essentially of a material selectedfrom the group consisting of silicon oxide, silicon carbide, zirconiumoxide, and aluminum oxide.
 7. The device according to claim 1, furthercomprising a main exhaust mechanism configured to exhaust said pressurereduced space, and a switching portion configured to selectively connectsaid buffer space to either one of said buffer exhaust mechanism andsaid main exhaust mechanism.